forms: Fix MultipleBooleanField.to_python when the field value is missing

If you write a test for, say, the bundle form of a patch list, you'd
still have to specify the 'no change' value to other form (e.g. the
multiple update one) fields using MultipleBooleanField or else it'd
raise a ValueError when field.clean() is called as part of
form._get_errors().

Signed-off-by: Guilherme Salgado <guilherme.salgado@linaro.org>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/apps/patchwork/forms.py b/apps/patchwork/forms.py
index 3d3abb3..1ff2bd0 100644
--- a/apps/patchwork/forms.py
+++ b/apps/patchwork/forms.py
@@ -185,8 +185,8 @@ class MultipleBooleanField(forms.ChoiceField):
         return False
 
     def to_python(self, value):
-        if self.is_no_change(value):
-            return value
+        if value is None or self.is_no_change(value):
+            return self.no_change_choice[0]
         elif value == 'True':
             return True
         elif value == 'False':